My 2003 3.0 v6 has been running just fine for the last 10 years. 64,000 miles. But recently one morning it had a rough start, I had to give it gas, and it sputtered to life. The next day, the check engine light came on.

P0172 and P0175, system too rich, both banks.

I'm getting terrible mileage (even worse than normal in this gas hog), and this morning it was really, really hard to start. It took 5 minutes of turning over and pumping the gas pedal to get it to fire up.

I finally got an app to go with my bluetooth OBD reader and took some readings. Here are screenshots of the live sensor data: Sensor Readings - Imgur

What I think I know:
-Long Term Fuel Trim on both banks is maxed out in the negative, meaning the system is actually too rich and not just a faulty sensor alone.
-Bank 1 Sensor 2 Oxygen Sensor Output voltage is zero. Flat-out zero. That's bad, right?

What I'm wondering:
-I'm only getting readings from 3 O2 sensors. Aren't there four?
-If B1S2 O2 voltage is zero, is that a cause or a symptom of the too-rich environment?

Sparkplugs and wires are original. Coolant might be a little low. Air filter is new (replaced after engine light came on). I ran the last tank through with a full bottle of Seafoam.

I'm wondering where you guys think I should start investing money first--in sensors, plugs, wires, or injectors. I'm handy enough and I'm broke, so I'd like to be as strategic as possible as to where I drop cash.

Thanks in advance. Forums like these have made "being handy" possible for tools like me.

as for your 02 sensors there are only 3 of them 1 on each manifold and 1 right after the catalytic converter which is your bank 1 sensor 2 and all it does is monitor the converter to make sure it is functioning correctly

on a side note I've also been told it is pointless to pump a EFI vehicle